1. Field of the Invention
This invention is related to a single-phased electromagnetic actuator including a stator structure having two stator parts provided on both sides of a thin magnetized portion of an angularly movable member.
2. Discussion of the Background
An electromagnetic actuator as above-noted is disclosed in the International Patent Application CH-8 700 063 filed June 1, 1987 on the priority of the Swiss Patent Application No. 22,886 filed June 2, 1986. In the electromagnetic actuator disclosed in this International Application, each of the stator parts is formed with a very high magnetic permeability material. At least one of these parts has 2N+1 magnetic poles of which one half is energized by an electrical coil. The thin portion includes 2N pairs of magnetized poles which are transversally magnetized and alternate in the angular motion direction. The thin magnetized portion has through the whole working range a substantially linear demagnetization characteristic. Such electromagnetic actuators as above-noted allow the movable member to move within a limited distance with a substantially constant strength. Such apparatus, however, has a major drawback. In effect, the magnetic circuit closing must necessarily be done by means of magnetic seals provided either in the stator structure rear part, namely perpendicular to the displacement path of the movable member, or in some planes being parallel to the displacement path of the movable member. This results in a significant increase of the overall space required by the stator structure.
The overall space requirements for these actuators are increasingly critical, and a number of applications require an extreme miniaturization not compatible with the embodiments of the apparatus such as known in the prior art.